Sex-related differences in sweat gland cholinergic sensitivity exist irrespective of differences in aerobic capacity.

Mechanisms accounting for sex-related differences in the sweat response remain to be elucidated. In the present study, we focused on differences in sweat gland cholinergic sensitivity between males and females. Since, males usually possess higher aerobic capacity than females, we investigated sweating in males and females grouped according to aerobic capacity (.VO(2peak)). Forty-four subjects were assigned to four groups: males with higher (MH) and lower (ML), and females with higher (FH) and lower (FL) .VO(2peak). Forearm sweating was induced by iontophoretic administration (1.5 mA, 60 muA cm(-2), 5 min) of pure water or varying concentrations of pilocarpine hydrochloride (0.125, 0.250, 0.5, 1.0 and 2.0%). Local sweat rate (absorbent paper) and the number of activated sweat glands (iodine impregnated paper) were computed. Maximal pilocarpine-induced sweat rate (SR(max)) and the pilocarpine concentration which elicited 50% of maximal sweating response (K (m)) were calculated. Sweat rate and active gland density increased in response to greater doses of pilocarpine (p < 0.05). Inter-group differences were evident: SR(max) was greatest for MH and lowest for FL (p < 0.05), but no significant differences were observed between ML and FH (p = 0.24). Higher SR(max) were observed, within-sex, for those with greater aerobic capacity (p < 0.05). Furthermore, males' K (m) values were higher than females', indicating greater sweat gland affinity for pilocarpine even for groups having similar aerobic capacity (p < 0.05). In summary, we confirmed that the human sudomotor response is affected by aerobic capacity but, also, that sex-related differences in sweat gland cholinergic sensitivity exist and are not necessarily associated with the typical differences in .VO(2peak) observed between sexes.

Distribuição regional do suor durante exercício progressivo até a fadiga / Sweat regional distribution during progressive exercise until fatigue

A partir da hipótese evolutiva de que a cabeça humana precisa ser resfriada de forma especial, o objetivo do presente estudo foi verificar se a sudorese seria maior na testa do que nas demais regiões do corpo durante o exercício progressivo até a fadiga (EPF). Em 17 voluntários (23 ± 2 anos, 76,93 ± 7,74 kg, 179 ± 7 cm e 1,9 ± 0,1 m²) foram medidos a taxa de sudorese local (TSlocal), o número de glândulas de suor ativas (GSA) e taxa de suor por GSA (TSlocal.GSA-1) em oito regiões do corpo (testa, costas, peito, braço, antebraço, mão, coxa e perna) durante o EPF em cicloergômetro. A TSlocal da testa foi maior que todas as outras regiões e a TSlocal do peito foi maior apenas que a da coxa. O número de GSA da testa foi maior do que em todas as outras regiões, e a GSA da mão foi maior que do peito, braço, coxa e perna. A TSlocal.GSA-1 da testa foi maior do que as do braço, antebraço, mão e coxa, e a TSlocal.GSA-1 das costas e do peito foram maiores que do antebraço e mão. A produção de suor da parte superior do corpo (testa, costas, peito, braço, antebraço, mão) foi maior que a inferior (coxa e perna). Concluiu-se que o EPF desencadeou um padrão de produção de suor maior na cabeça que pode estar relacionado à maior convecção nas regiões mais altas do corpo.

Considering the hypothesis of human selective brain cooling during exercise should depend on greater sweating mechanism in the forehead. The purpose of this study was verify variations of sweat production between body regions during progressive exercise until fatigue (PEF). Seventeen subjects (23 ± 2 years old, 76.93 ± 7.74 kg, 179 ± 7 cm and 1.9 ± 0.1 m²) volunteered for this study. Local sweat rate (STlocal), number of active sweat glands (ASG) and sweat rate for ASG (STlocal.ASG-1) in eight body regions (forehead, back, chest, arm, forearm, hand, leg and calf) were measured during PEF in cyclergometer. The STlocal of the forehead was higher than in all others regions and the chest STlocal was higher only than the leg. The number of ASG in the forehead was greater than in all other regions, and the ASG of the hand was higher than those of the chest, arm, leg and calf. The STlocal.ASG-1 of the forehead was higher than the arm, forearm, hand and leg, and the STlocal. ASG-1 of the chest and back were higher than the forearm and hand. The sweat production of the upper body (forehead, back, chest, arm, forearm and hand) was bigger than the lower body (leg and calf). In conclusion, the PEF promoted a sweating pattern in body regions that can be related to the higher convection present in the upper regions of the body.